In the intake watercourse for the hydro power station, entrance of the river fish, such as Ayu, into the intake watercourse may cause problems such as compensation for the river fish.
Conventionally, therefore, a net has been installed near the intake hole of the hydro power station to prevent the entrance of fish, and the interception of the entrance of the fish has been achieved by such net.
In the case of conventional interception by said net, however, the entrance of considerably small fish must be intercepted and therefore a fine-mesh net must be used. This net, however, has such disadvantage as it is easy to break and the interception of fish cannot be secured.
Furthermore, there is another problem that fish may be trapped by said net and the meshes of said net are plugged thereby.